Salicylic acid is a common ingredient in many over-the-counter skin care products, particularly those targeting acne, but its role in managing eczema is more nuanced. Eczema, or atopic dermatitis, is a chronic inflammatory skin condition characterized by an impaired skin barrier, leading to dryness, redness, and itching. Salicylic acid, which is derived from willow bark, is a topical agent used primarily for its exfoliating properties.
Understanding Salicylic Acid’s Mechanism
Salicylic acid functions as a keratolytic agent. The chemical works by directly solubilizing the intercellular cement that holds skin cells, or corneocytes, together. By disrupting the cellular junctions, the acid promotes the desquamation, or shedding, of the horny layer. This desmolytic property helps to thin thickened areas of skin without affecting the underlying, viable epidermis. Salicylic acid modifies the pH of the stratum corneum, creating an acidic environment that assists in softening hyperkeratotic areas.
When Salicylic Acid Helps Eczema Symptoms
Salicylic acid is not recommended for the treatment of acute, inflamed, or weeping eczema due to its potential to cause irritation on already compromised skin. The exfoliating action can further damage the impaired skin barrier typical of active atopic dermatitis, worsening inflammation and sensitivity. However, this ingredient can be beneficial for chronic eczema patches that have become thick, leathery, and scaly, a condition known as lichenification or hyperkeratosis. The keratolytic action helps to break down the dense, built-up layers of dead skin cells in these chronic plaques.
By softening and removing the scaling, salicylic acid can reduce the rough texture and thickness of the lesions. This preparatory action allows other topical medications, such as corticosteroids or emollients, to penetrate the skin more effectively. For example, in conditions like seborrheic dermatitis, a type of eczema characterized by flaking, salicylic acid shampoos and facial products are often recommended to lift and remove scales. The acid manages a common consequence of long-term eczema, the thickening of the skin, rather than treating the underlying immune-driven inflammation itself.
Guidelines for Safe Application
The safe use of salicylic acid for eczema depends on selecting the correct concentration and applying it strictly to specific skin areas. For sensitive or eczema-prone skin, it is usually advisable to start with very low concentrations, typically 0.5% to 2% in over-the-counter products. Products in the form of ointments or lotions containing 2% to 3% salicylic acid may be suggested for psoriasis or hyperkeratotic eczema, especially when supervised by a healthcare provider. It is necessary to perform a patch test on a small, inconspicuous area of skin before applying the product more widely to check for irritation or allergic reactions.
Application should be limited to the thickened, intact patches of skin and should not be applied to open wounds, infected lesions, or areas of active inflammation. To protect surrounding skin, applying a barrier like petroleum jelly around the periphery of the target area is recommended. Because salicylic acid can be drying, it is important to follow its application with a ceramide-rich moisturizer to support the skin barrier and counteract dryness. For conditions like seborrheic dermatitis on the scalp, medicated shampoos are often used to ensure the product is rinsed off, minimizing contact time and irritation.
Side Effects and Safety Considerations
The most common side effects associated with topical salicylic acid use include mild stinging, burning, redness, and dryness, particularly when higher concentrations are used or if the product is applied to broken skin. If severe irritation or a flare-up of eczema occurs, the product should be discontinued or the application frequency should be reduced. Systemic salicylate toxicity, also known as salicylism, occurs when the chemical is absorbed through the skin in excessive amounts.
The risk of salicylism increases when high concentrations are applied over a large body surface area, under occlusion, or to extensively damaged skin, as the impaired barrier allows for greater absorption. Symptoms of systemic toxicity can include ringing in the ears (tinnitus), rapid breathing (tachypnea), vomiting, and an altered mental status. Caution is required when using salicylic acid on children, who are more susceptible to irritation and have a greater risk of absorption. Topical salicylic acid is generally not used in children younger than two years old.